adding scenes into blender video duplicates soundtrack from original video
Laying text on top of a video strip in the VSE:

The VSE's built in Text tool?  That gave me no joy either so I do it this way...

In Blender's 3D window, press SHIFT-C to center the 3D cursor.

Add text for one of the subtitles and if there's no camera, add one of those also.  Ensure it is pointing straight down by pressing ALT-R.

View through the camera with Numpad-Zero key.  

In the 3D window press N to bring up the window's properties and open the "View" tab and tick "lock camera to view".  Close with N again and zoom the camera in and out so you can see all of the text.  (the "Home" key will automatically fit the view to the available space.
(You can alternatively scale the text)

Various fonts aren't hard to setup, but we'll get to that below.

When you get the text looking right, make a save of this Blender setup and use it as a template for future text image creation.

Render what's in the camera viewport and save it as an alpha layered image in .png format.

To do this go to the render properties at right, (ALT-SPACE) open up it's "Output" tab and nominate the folder for the image and set it to the png format.  Make sure to press the RGBA button at extreme right in order to add an alpha layer.

Whilst in the rendering properties, go to the "shading" tab  and set it's 'alpha' setting slot at right, from 'Sky' to 'Transparent'.

Render using OpenGL or with Blender's internal render.  I prefer OpenGL for this job.
Goto upper left of window and click on "Render-->OpenGL Render Animation"

By choice I'd be creating the text images in one Blender file and using another to produce the final mixed movie in the VSE to keep things straight forward and predictable.

Once the text images have been rendered, lay them over the main movie in the VSE where they're supposed to show.



You'll need to set each text strip as an "Alpha Over" in it's properties panel but read on beforehand.... 
(Highlite the strip &amp; press N)

The image strips can also be faded in and out by keyframing their opacity.  

Because you'll most likely have to position and scale the text, add an effects strip for each text image.
Select the text strip, press SHIFT-A and select "Effects strip-->Transform."

When you use Effects strips, it's best to leave the text properties alone and set Location, Scale, and Opacity settings in the Effects-strip properties instead. (at right when you press N)

The movie along with subtitles can now be rendered.  The VSE will render this arrangement up quite rapidly compared to the method you have been using.  



Fonts:

You can use most fonts that Windows does.  Simply goto the C:\Windows\Fonts folder and copy those you like into Blender's Fonts folder.  That's found in -

C:\Blender277\blender-2.77a-windows64\2.77\datafiles\fonts\

Once you've got a selection of fonts -

Select the text properties at right (F icon) and open the Font tab, click on the "Regular" folder, and select from those you've copied across.

Saving Blender in various setup configurations, will retain all your settings and likes, ready to be used at any time.

Colours and/or textures for added text objects can be set up as with any object.